System and method for providing parallel power in a hybrid-electric vehicle

ABSTRACT

An aspect of the present invention involves a system and method for providing parallel power in a hybrid-electric vehicle. The system includes a compact motor coupled to the input shaft of the vehicle&#39;s transmission. Advantageously, the compact motor and the engine use the same drivetrain. Both the compact motor and the engine are able to apply power to the portion of the drivetrain from the transmission to the wheels. Since the motor is compact and does not require a separate drivetrain, the parallel power system can be installed in an otherwise conventional vehicle without packaging difficulties.

BACKGROUND OF THE INVENTION

[0001] The field of the invention relates to systems and methods forproviding parallel power in a hybrid-electric vehicle.

[0002] Hybrid electric vehicles (HEVs) combine the internal combustionengine of a conventional vehicle with the battery and electric motor ofan electric vehicle, and provide better fuel economy than comparableconventional vehicles. This combination offers the extended range andrapid refueling that consumers expect from a conventional vehicle, witha significant portion of the energy and environmental benefits of anelectric vehicle. The practical benefits of HEVs include improved fueleconomy and lower emissions compared to conventional vehicles.

[0003] A hybrid's efficiency and emissions depend on the particularcombination of subsystems, how these subsystems are integrated into acomplete system, and the control strategy that integrates thesubsystems. Existing HEVs use complex integration systems, which, whileefficient, have not yet proven to be economically feasible. Thecommercial success of HEVs has been hindered by the economics ofproducing a complex hybrid power system rather than by the inherentcapabilities of the technology. Complexity is a major disadvantage ofexisting HEV configurations, and has inhibited the acceptance of HEVs inthe marketplace.

[0004] HEV configurations fall into two basic categories: series andparallel. In a series hybrid, the internal-combustion engine drives agenerator that charges the batteries, which power an electric motor.Only the electric motor can directly turn the vehicle's wheels to propelthe vehicle. In contrast, in a parallel hybrid either the engine or themotor can apply torque to the wheels. Both the parallel and the serieshybrid can be operated with propulsion power supplied only by theinternal-combustion engine. But in a series hybrid, this power isinefficiently applied through the generator and the electric motor.Parallel HEVs do not require a generator, because the motor generateselectricity when driven by the engine. Parallel HEVs are thus lesscomplex than series HEVs. Another advantage of the parallel scheme isthat a smaller engine, electric motor, and battery pack can be used,because the engine and the motor work together to drive the vehicle.

[0005] Turning to series HEVs, an advantage of series configurations isthat the internal-combustion engine can be located anywhere in thevehicle because it does not transmit power mechanically to the wheels.This is advantageous for designing the vehicle because the designer hasmore freedom of choice in determining where the internal combustionengine should be located. In contrast, parallel configurations mustconnect both the motor and the engine to the drivetrain. This requiresthe motor and the engine to be in proximity to each other. Thoughparallel configurations are generally preferred for their flexible poweroutput, the difficulty of packaging both a conventional engine and aconventional electric motor in a drivetrain has been a majordisadvantage of existing parallel HEVs.

SUMMARY OF THE INVENTION

[0006] An aspect of the present invention involves a system and methodfor providing parallel power in a hybrid-electric vehicle. The systemincludes a compact motor coupled to the input shaft of the vehicle'stransmission. Advantageously, the compact motor and the engine use thesame drivetrain. Both the compact motor and the engine are able to applypower to the portion of the drivetrain from the transmission to thewheels. Since the motor is compact and does not require a separatedrivetrain, the parallel power system can be installed in an otherwiseconventional vehicle without packaging difficulties.

[0007] Other and further objects, features, aspects, and advantages ofthe present invention will become better understood with the followingdetailed description of the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

[0008] The following drawings illustrate both the design and utility ofpreferred embodiments of the invention.

[0009]FIG. 1 is a top diagram view of a hybrid electric vehicleconstructed in accordance with an embodiment of the present invention.

[0010]FIG. 2 is a front perspective view of a compact electric motorconstructed in accordance with an embodiment of the present invention.

[0011]FIG. 3 is a schematical view of a system constructed in accordancewith an embodiment of the present invention for providing parallel powerin a hybrid-electric vehicle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012]FIG. 1 shows a diagram of a parallel hybrid electric vehicle (HEV)10 constructed in accordance with an embodiment of the presentinvention. The vehicle 10 comprises an engine 20, a coupling 30, acompact motor 40, a transmission 50, fuel tanks 60, auxiliary components70, an inverter system 80, drive shaft 90, differential 100, wheels 110,and an energy storage pack 120. A parallel hybrid electric drivetrain122 may include one or more of the engine 20, the coupling 30, thecompact motor 40, the transmission 50, the drive shaft 90, and thedifferential 100.

[0013] The vehicle 10 shown in FIG. 1 is a heavy-duty vehicle. Aheavy-duty vehicle is preferably a vehicle having a gross vehicle weight(GVW) of at least 10,000 lbs. Examples of heavy-duty vehicles that theparallel hybrid electric drivetrain 122 may be used with include, butnot by way of limitation, a tractor, a tow tractor, a tug, a pulltractor, a push-back tractor, a truck (e.g., class 6, class 7, class 8,etc.), a dump truck, a semi truck, a bobtail truck, a school bus, atransit bus, a pick-up truck, a shuttle van, a refuse-collectionvehicle, a recycling-collection vehicle, and a tram vehicle. Theparallel hybrid electric drivetrain 122 may be used with vehicles otherthan heavy-duty vehicles, and, thus, is not limited to heavy-dutyvehicles.

[0014] The engine 20 may comprise a spark ignition engine, compressionignition engine, turbine engine, or any other engine that transmitspower through a rotating shaft. The coupling 30 couples the engine 20 tothe compact motor 40. The coupling 30 is preferably capable ofconnecting and disconnecting the engine power from the compact motor 40.The coupling 30 may include, but is not limited to, a clutch, torqueconverter, or positive mechanical link. In FIG. 1, the coupling 30 isunderstood to be housed in a bellhousing. The HEV system is a parallelsystem, meaning that the engine 20 and compact motor 40 cansimultaneously provide power to the drivetrain, and thus to the wheels110.

[0015]FIG. 2 shows an embodiment of a compact motor 40 constructed inaccordance with the present invention. The compact motor 40 ispreferably a pan-type motor to minimize axial length. It is to beunderstood that motor specifications will vary with vehiclerequirements, with smaller vehicles typically requiring smaller motorsand larger vehicles normally requiring larger motors. The compact motor40 shown in FIG. 2 is illustrative of compact motors adapted for use inheavy duty HEVs. The compact motor 40 is eighteen inches in diameter,four inches long, and meets the following specifications:

[0016] Motor Type: PM Brushless DC

[0017] Maximum Torque: 1000 Nm@250 Arms/ph for 2 min.

[0018] Maximum speed: 2500 rpm

[0019] Peak efficiency: 92%

[0020] Coolant: Weg 50

[0021] Coolant flow rate: 5 gpm

[0022] Pressure drop: 5 psi

[0023] Max. Inlet temperature: 75 C.

[0024] Max. Ambient temperature: 65 C.

[0025] Weight: 95 lb

[0026] A suitable liquid cooled traction motor is available fromPrecision Magnetic Bearing Systems, Inc. of Cohoes, N.Y. Such pan-typemotors use powerful permanent magnets to reduce size, and employthin-stator designs to allow the motors to be compact.

[0027] In heavy-duty embodiments comprising digital controller areanetworks (CANs), the compact motor 40 is preferably driven by a 250 kWCANverter inverter 80. When used with the compact motor 40 specifiedabove, the inverter 80 preferably meets the following specifications:

[0028] Motor Options: PM Brushless or AC

[0029] Continuous Power: 250 kW

[0030] Input Voltage: 600 Vdc

[0031] Output Current (Apk/ph.): 600A@25 C.; 420A@70 C.

[0032] Peak Efficiency: 97.50%

[0033] Coolant: Ethylene/Glycol 50-50

[0034] Coolant Flow: 5 gpm

[0035] Pressure Drop: 5 psi

[0036] Inlet Temperature: 167° F. (75° C.)

[0037] Size: 14.4×8.7×4.2 in

[0038] Weight: 27 lbs (12 kg)

[0039] A suitable CANverter inverter 80 is available from PrecisionMagnetic Bearing Systems, Inc. of Cohoes, NY. It is to be understoodthat inverter specifications will vary with motor requirements.

[0040] Since the compact motor 40 can provide power to the drivetrain,the engine 20 can be reduced in size proportionally to the output of themotor 40. For instance, given the specifications above, the heavy-dutyHEV would have approximately two-hundred additional horsepower when thecompact motor 40 was providing full assist. If the engine in acomparable conventional vehicle produced, for instance, four-hundredhorsepower, the engine 20 in the embodiment described above need onlyproduce half as much power. Lower power requirements permit the use ofsmaller, less polluting, more efficient engines.

[0041] The transmission 50 is preferably an automated manual shifttransmission (shift by wire). Also, in this embodiment, the coupling 30can be a conventional clutch mechanism (including flywheel), or it canbe a positive mechanical link. The clutch may be optional during usebecause at low speeds, the engine is preferably off, and the motor isdriving the vehicle. Therefore, engine stalling is not an issue. Thoughdisengaging a clutch during motor-only operation would advantageouslyprevent the motor from spinning the engine, re-engaging the clutch whilemoving would likely jerk the vehicle, similar to a push start.Nevertheless, a clutch would be advantageous in applications where thevehicle operates at very low, motor-only speeds for extended lengths oftime (so the motor would not have to expend energy spinning the engine).

[0042] In applications where no clutch is used, the motor 40 turns theengine 20 without injecting fuel until the engine speed reachesapproximately 1000 RPM. The engine 20 starts immediately when fuel isintroduced into the engine 20 when it is spinning at 1000 RPM. By notrunning the engine 20 at low speeds or at idle, noise and pollution isabated, and clutch wear is prevented. This embodiment requireselectrically driven accessories so that accessories can operate with theengine off.

[0043] By placing the coupling 30 between the engine 20 and the compactmotor 40, the motor is capable of operating independently of the engine,for instance when the coupling 30 comprises a disengaged clutch. It isalso advantageous to place the coupling 30 between the engine 20 and themotor 40 to move the motor 40 away from the heat and vibration of theengine 20.

[0044] In various embodiments, the energy storage pack 120 may include,but is not limited to, ultracapacitors, high power prismatic NIMHbatteries, or lead-acid batteries. The compact motor 40 preferably alsoacts as a generator to charge the energy storage pack 120. The compactmotor 40 generates electricity during regenerative braking, and asneeded by spinning the motor with energy from the engine. Regenerativebraking also reduces wear on brake components.

[0045] Though it is desirable to convert vehicles to parallel HEVs,converting a conventional vehicle to a parallel HEV has, until now,proven to be expensive and time consuming. For instance, the paralleldrive systems produced by Allison Transmission and Enova require manynew components and significant changes to the drivetrain. Similarly, theparallel drive systems employed in the Toyota Prius and Honda insightare vehicle specific; entirely new vehicles were built around the HEVcomponents.

[0046] In contrast to the existing expensive and time consuming systemsand methods for converting vehicles to parallel HEVs, the presentinventor has found that conventional vehicles can be easily convertedinto parallel HEVs by installing a compact motor 40 between the coupling30 and the transmission 50.

[0047] The process of converting a conventional vehicle to a parallelHEV according to an embodiment of the present invention comprises thefollowing steps: removing the transmission 50 and driveshaft 90;replacing the transmission input shaft with one that is long enough toaccommodate the additional axial length of the compact motor 40;providing a compact motor 40 that is machined on one side to mount tothe transmission, and is machined on the other side to mount to thebellhousing; assembling the compact motor 40 to either the transmission50 or the bellhousing; reinstalling the transmission in the vehicle; andreplacing the driveshaft 90 with one that is shortened appropriately tocompensate for the offset of the transmission 50. Once the compact motor40 is installed, a conventional HEV control system, energy storagesystem, and inverter are utilized to complete the conversion.

[0048] Though a retrofit application is discussed above, it is clearthat the design principles of the present invention could easily beapplied to original equipment manufacturing (OEM) applications. Forinstance, original equipment manufacturers are motivated to continueusing existing parts when possible; redesign and retooling areexpensive. The present invention is advantageous in both aftermarket andOEM contexts because it provides a system for converting currentproduction drivetrains to parallel HEV drivetrains with a minimal numberof new parts or design changes.

[0049] With reference to FIG. 3, an embodiment of a parallel hybridelectric drivetrain and control system 124 will now be described. Inthis embodiment, a 330 horsepower internal combustion engine 125 isconnected in parallel with a compact 140 Kw electric motor/generator126, which is mounted on one side to a seven-speed powershifttransmission 128. A vehicle dynamics controller 130 receives inputs fromvehicle systems 140 such as anti-lock breaking system (ABS) and speedsensors, and from driver interface 150, which may includeacceleration/braking, driver controls, and driver information. Based onthose inputs, the vehicle dynamics controller 130 controls powerdistribution between the engine 125 and the motor 126, and may provideinput to the transmission 128.

[0050] The vehicle dynamics controller 130 does not communicate directlywith the motor 126, but instead communicates with a motor controller160, in this case a 180 kVA motor controller 160. Also in communicationwith the motor controller 160 is the energy storage system 170, which ismanaged by an energy management system 180. The energy storage system170 in this embodiment comprises between 28 and 50 twelve volt batterieseach rated at 80-90 amp-hours, for approximately 40 kW/h of energystorage. Since batteries are used, a battery management system 190equalizes and maintains the batteries. The energy management system 180monitors the amount of power or energy available in the energy storagesystem 170, and provides this information to the vehicle dynamicscontroller 130. In vehicles utilizing SAE CAN J1939 networks, thevehicle dynamics controller 130 can be connected to the network,completing the system.

[0051] Although the present invention has been described above in thecontext of certain preferred embodiments, it is to be understood thatvarious modifications may be made to those embodiments, and variousequivalents may be substituted, without departing from the spirit orscope of the invention.

What is claimed is:
 1. A parallel hybrid-electric vehicle drivetrain,comprising: a transmission; an electric motor connected with thetransmission to drive the transmission; and an internal combustionengine connected with the transmission to drive the transmission,wherein the electric motor is located between the internal combustionengine and the transmission.
 2. The drivetrain of claim 1, furtherincluding a coupling to couple the engine with the transmission to drivethe transmission, and the electric motor is located between the couplingand the transmission.
 3. The drivetrain of claim 1, wherein the atransmission includes an input shaft, the electric motor is connectedwith the input shaft of the transmission, the internal combustion engineincludes an output shaft, the drivetrain further includes a couplingconnecting the output shaft of the engine with the input shaft of thetransmission, and the electric motor is located between the coupling andthe transmission.
 4. The drivetrain of claim 1, wherein the electricmotor is a compact electric motor.
 5. A heavy-duty parallelhybrid-electric vehicle, comprising: a vehicle body; a plurality ofwheels; and a parallel hybrid-electric vehicle drivetrain to drive atleast two wheels of the plurality of wheels, the parallelhybrid-electric vehicle drivetrain including a transmission, an electricmotor connected with the transmission to drive the transmission, and aninternal combustion engine connected with the transmission to drive thetransmission, wherein the electric motor is located between the internalcombustion engine and the transmission.
 6. The vehicle of claim 5,wherein the vehicle has a GVW of at least 10,000 lbs.
 7. The vehicle ofclaim 5, wherein the vehicle is a member from the group consisting oftractor, a tow tractor, a tug, a pull tractor, a push-back tractor, atruck, a class 6 truck, a class 7 truck, a class 8 truck, a dump truck,a semi truck, a bobtail truck, a school bus, a transit bus, a shuttlevan, a refuse-collection vehicle, a recycling-collection vehicle, and atram vehicle.
 8. The vehicle of claim 5, further including a coupling tocouple the engine with the transmission to drive the transmission, andthe electric motor is located between the coupling and the transmission.9. The vehicle of claim 5, wherein the a transmission includes an inputshaft, the electric motor is connected with the input shaft of thetransmission, the internal combustion engine includes an output shaft,the drivetrain further includes a coupling connecting the output shaftof the engine with the input shaft of the transmission, and the electricmotor is located between the coupling and the transmission.
 10. Thevehicle of claim 5, wherein the electric motor is a compact electricmotor.
 11. A method of converting an internal-combustion engine vehicleinto a parallel hybrid-electric vehicle, the internal-combustion enginevehicle including an internal combustion and a transmission, the methodcomprising the steps of: removing the transmission from the vehicle;installing an electric motor into the vehicle; coupling the electricmotor to the internal-combustion engine; installing the transmissioninto the vehicle so that the electric motor is between the internalcombustion engine and the transmission; and coupling the motor to thetransmission.
 12. The method of claim 11, wherein the vehicle is aheavy-duty vehicle.
 13. The method of claim 12, wherein the vehicle hasa GVW of at least 10,000 lbs.
 14. The method of claim 12, wherein thevehicle is a member from the group consisting of tractor, a tow tractor,a tug, a pull tractor, a push-back tractor, a truck, a class 6 truck, aclass 7 truck, a class 8 truck, a dump truck, a semi truck, a bobtailtruck, a school bus, a transit bus, a shuttle van, a refuse-collectionvehicle, a recycling-collection vehicle, and a tram vehicle.
 15. Themethod of claim 11, wherein the electric motor is a compact electricmotor.
 16. The method of claim 11, wherein the electric motor includes afirst axial length, the internal-combustion engine vehicle furtherincludes a bellhousing, a first driveshaft, and the transmissionincludes a first input shaft, the method further comprising the stepsof: removing the first driveshaft from the vehicle; removing the firstinput shaft from the transmission; providing a second input shaft, thesecond input shaft being longer than the first input shaft by an amountcorresponding to the first axial length; installing the second inputshaft into the transmission; installing an electric motor includesinstalling an electric motor with a with a first side and a second side,wherein the first side is adapted to be mated to the transmission, andthe second side is adapted to be mated to the bellhousing, the electricmotor further adapted to provide torque to the second input shaft;mating the electric motor to the bellhousing; providing a seconddriveshaft, the second driveshaft being shorter than the firstdriveshaft by an amount corresponding to the first axial length;installing the second driveshaft into the vehicle.